This invention relates to an electron beam exposure apparatus and method of controlling the same. More particularly, the invention relates to an electron beam exposure apparatus for drawing a pattern on a wafer directly or on a mask or reticle using a plurality of electron beams, a method of controlling the apparatus, the associated control program and a method of manufacturing a device using this electron beam exposure apparatus.
Examples of electron beam exposure apparatuses include an apparatus of the point beam type which uses a beam in the shape of a spot, an apparatus of the variable rectangular beam type which uses a beam in the shape of a rectangular cross section, and an apparatus of the stencil mask type which uses a beam given a desired cross sectional shape through the use of a stencil mask.
The electron beam exposure apparatus of the point beam type is used exclusively for research and development purposes because of its low throughput. Though the electron beam exposure apparatus of the variable rectangular beam type has a throughput higher than that of the apparatus of the point beam type by one to two orders, many problems remain in terms of throughput when it is attempted to expose a pattern consisting of fine patterns on the order of 0.1 .mu.m integrated to a high degree. On the other hand, the electron beam exposure apparatus of the stencil mask type uses a stencil mask in which a plurality of repetitive pattern through-holes are formed at a portion thereof that corresponds to a variable rectangular aperture. As a result, the electron beam exposure apparatus of stencil mask type is highly advantageous when exposing repetitive patterns. However, in the case of a semiconductor circuit that requires a multiplicity of transfer patterns that will not fit on a single stencil mask, it is necessary to produce a plurality of stencil masks in advance and use them by extracting them one at a time. Since changing masks takes time, a problem that arises is a very low throughput.
An apparatus which solves this problem is a multi-electron beam exposure apparatus which irradiates the surface of a sample with a plurality of electron beams along design coordinates of the surface, scans the plurality of electron beams across the sample surface by deflecting the electron beams along the design coordinates, and turns the plurality of electron beams on and off individually in conformity with the pattern to be drawn, thereby drawing the pattern on the surface. A feature of the multi-electron beam exposure apparatus is that throughput can be improved owing to the ability to draw any pattern without using a stencil mask.
FIG. 18A illustrates the general arrangement of the multi-electron beam exposure apparatus. The apparatus includes electron guns 501a, 501b, 501c whose electron beams can be turned on and off individually, a reduction electron optical system 502 for reducing the diameters of the plurality of electron beams and projecting the beams upon a wafer 503, and a deflector 504 for scanning the plurality of projected electron beams of reduced diameter across the wafer 503.
As shown in FIG. 18B, electron beams B1, B2, B3 from the electron guns 501a, 501b, 501c, respectively, are deflected equal amounts by the deflector 504. As a result, with the respective beam reference positions serving as the reference, the electron beams are moved while their positions on the wafer are set successively in accordance with arrays (element exposure areas) decided by the deflector 504. More specifically, FIG. 18B shows the manner in which patterns to be exposed are exposed in accordance with identical arrays. Each of the electron beams is moved while its position is set in such a manner that the positions on the arrays at identical times become (1,1), (1,2), . . . (1,16), (2,1), (2,2), (2,16), (3,1). Here element exposure areas ES1, ES2, ES3 exposed by respective ones of the electron beams are decided by the deflector 504, with the element exposure areas being contiguous. By deflecting the electron beams and controlling irradiation by the electron beams, patterns (P1, P2, P3) to be exposed are exposed in the respective element exposure areas.
There are instances where it is attempted to expose a continuous pattern P0 of the kind shown in FIG. 18B composed of the patterns P1, P2, P3 exposed by the electron beams B1, B2, B3. However, there are occasions where the element exposure areas ES1, ES2, ES3 are not contiguous and move apart from each other, as shown in FIG. 18C, owing to the deflection precision of the deflector 504 or a change in the reduction electron optical system 502 with the passage of time. As a result, the pattern P0, which is to be continuous, is exposed upon being split up into non-contiguous patterns P1, P2, P3. Consequently, in a semiconductor device manufactured from a wafer on which such a pattern has been exposed, the desired operation cannot be achieved owing to severing of wiring, and there is a pronounced decline in the yield of the semiconductor device manufacturing process.